The present invention relates to a method and machine for the production of hollow articles from, for instance, plastic or glass in viscous condition, with at least one multiple mold comprising a plurality of mold elements into which gobs of plastic material are introduced into the mold elements to be subsequently formed and expanded to finished hollow articles.
In a known method of the aforementioned kind disclosed for instance in FIGS. 7 and 8 of U.S. Pat. Nos. 3,951,637 and 4,057,412 of the same inventor, the center distance of the mold elements of each multiple mold remains constant during the whole operating cycle. The magnitude of this distance depends on the maximum transverse dimension, for instance, the diameter of the finished hollow article. During the last years the center distance of mold elements of multiple molds in machines for the production of hollow glass articles has been continuously increased because such glass articles have been produced with ever increasing transverse dimensions. This, however, entailed a corresponding considerable increase of the necessary expenditure, the necessary operating force and the required space for the total machine. It should be noted that in such machines the relatively large center distance of the mold elements of the multiple mold is only necessary during the final phase of the production of the hollow glass articles, that is when the latter reach their maximum transverse dimensions. In all preceding phases of the operating cycle, such a large center distance which requires the aforementioned high expenditure, driving force and space requirement are not necessary. It is further of disadvantage that the known machines have to be designed for a hollow article with a predetermined maximum transverse dimension. If it is now desired to produce hollow articles of a transverse dimension greater than the predetermined maximum transverse dimension, then it has up to now been the practice to reduce the wall thickness of the finish molds below the optimum value. This, in turn created thermal and technological problems leading to defects in the finished articles.